1. Field of the Invention
This invention related in general to the absorption of certain organic molecules in hydrocarbon block copolymers. In one aspect, this invention is directed to a method for the absorption of hydrocarbons, chlorocarbons and other non-polar molecules in certain hydrocarbon block copolymers. In another aspect this invention is directed to environmentally beneficial separation and/or recovery systems which utilize hydrocarbon block copolymers as absorbents for hydrocarbons, chlorocarbons and other non-polar organic molecules. In a further aspect, the invention is directed to an apparatus which utilizes hydrocarbon block copolymers for the absorption of such molecules.
2. Background Art
A wide variety of materials have been employed in recent years as absorbents for various chemicals, gases, toxic wastes, and the like. In view of the trend towards an environmentally safe atmosphere, continous efforts are being expended to provide processes and equipment for the entrapment, separation, recovery and safe disposition of chemicals and toxic substances which heretofore had merely been released to the atmosphere or improperly buried in landfills. Accordingly, most industries today have undertaken programs and employ expensive absorption systems to prevent undesirable products from escaping from their plants which might otherwise pollute the air, land or water.
The literature is therefore replete with methods, processes, filtering equipment, absorbents, and numerous other recovery and separation systems for preventing the escape of toxic materials into the atmosphere. One of the more popular mediums which has been used to absorb materials, is granular activated carbon. However, more recent developments have been directed to a variety of new absorption materials which have a greater absorption capacity per unit weight, are less expensive and are more easily disposed of, for example, by incineration at a waste-to-energy cogeneration plant.
Attempts have been made recently to employ certain organic polymeric materials to avoid the deficiencies of absorbents, such as activated carbon. These materials are generally produced either as large pellets which are mechanically easy to use but which have very low surface areas and therefore have very limited use in absorbing materials from dilute streams in water or air. Another form in which certain of the newer absorbents are employed is an aggregation of very small spheres. While they have an adequate surface area, the use of the very small spheres suffers from a number of disadvantages for use as absorbents.
First, the absorption media is an aggregates of very small spheres. These aggregates can be broken up by severe pressure or turbulance or abrasion and the resulting particles are so small that they may leave or plug the absorption column or bed.
Second, like the large pellets they have soft segments and are deformable. This softness and the ease of deformation increase as the so called soft segment absorbs more hydrocarbon until the material can become tacky and flow and even liquify in the extreme. This means that under some conditions the bed or column may compact and form blockages or even conglomerates, lose surface area and in general become of relatively little value. This is particularly true if one tries to take the beds to very high loadings or if they are suddenly damaged by a slug of material, that is, high concentrations of hydrocarbon, chlorocarbon and the like, entering the bed.
Third, these copolymers are lower in density than water, and therefore in water usages they will float and must be constrained by filters. Filters in turn can be plugged by fines and soft, larger particles from the bed. Attempts have been made to minimize some of these characteristics and provide some mechanical support to an absorption bed comprised of copolymers by using some sort of harder less compressable spacer material. Activated carbon has been used for this purpose and the composite bed of carbon and copolymer particles is useful in certain practical separations. However, the unfavorable characteristics of the copolymers are only slightly modified by using carbon as spacers. Another disadvantage of the copolymer materials is that they can not be regenerated with heat; in most cases raising the temperature of the saturated hydrocarbon or chlorocarbon saturated hydrocarbon block copolymer bed promotes the softening of the copolymer and in most cases would lead to an aggregation of the bed and destruction of any useful properties. So in general many of these polymer material are not regenerated but are formulated to be disposed of by incineration or as landfill.
These copolymers can be melted and extruded in any sort of film or rod or any other extrusion shape which is desired. The product can be either cut up or formed into absorption material which can be packed in a bed as a sort of fabricated filter device. However, the inate softness of the material when it become loaded with organics would prevent these shapes from having the required rigidity and lack of compressibility and stickiness that is desired except under unusal conditions, that is, where the total amount of hydrocarbon to be absorded is very low and an efficient filter made of extruded fine diameter fibers of copolymer could be fabricated into an efficient web or composite that would have a high surface area and be capable of absorbing small amounts of hydrocarbons or other contaminants in devices which require very low pressure drops, such as air conditioning systems. Hence, to date the use of copolymer materials as absorbents has not been without its problems.
It has now been found that by using certain elastomeric or hydrocarbon block copolymer materials, as hereinafter defined, a wide variety of chemicals, such as, benzene, naphthalene, toluene, PCB's, xylene, isooctane, vinyl halides, gasoline, deisel fuel, chlorobenzene, perchloroethylene, methyl-t-butyl ether, trichloroethylene, isoprene, and numerous other relatively non-polar compounds whose solubility parameters are close to those of the soft or amorphous block of the hydrocarbon block copolymers, can be separated from gaseous and/or liquid streams with significant reductions in both cost and frequency of absorption media replacement. The use of these elastomeric polymeric materials allows for the reduction in absorption bed size, extended life of the absorption media and environmentally safe disposition of the absorbed material.
It is therefore and object of this invention to provide a method and apparatus for the absorption of non-polar organic molecules from fluids. Another object of this invention is to provide a process for removing undesirable contaminants from gaseous and liquid industrial waste streams. Another object of this invention is to remove gasoline, diesel fuel and other organic contaminants. A further object is to provide a method which is environmentally attractive for the separation of toxic substances from the effluent of chemical processes. A still further object of the invention is to provide substrates, such as fibrous substrates, coated with an absorbent hydrocarbon block copolymer which is highly efficient and selectively in absorbing non-polar organic materials.
These and other objects will be readily apparent to those skilled in the art in light of the teachings herein set forth